<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    *{
      margin:0;
      padding:0;
    }
    .container{
      height:200px;
      background-color: #ccc;
      min-width: 500px;
    }
    .main {
      width:100%;
      height:200px;
      background-color: #00f;
      float: left;
    }
    .left,.right{
      /* position: absolute; */
      float: left;
      width:200px;
      height:200px;
      background-color: #f00;
    }
    .left{
      margin-left:-100%;
    }
    .right{
      margin-left:-200px
    }
    .main_w{
      margin: 0 200px;
    }
    
  </style>
</head>
<body>
  <div class="container">
    <div class="main">
      <div class="main_w">1</div>
    </div>
    <div class="left">2</div>
    <div class="right">3</div>
  </div>
</body>
</html>